Comparative studies on actin include an attempt to complete the amino acid sequence of actin from Acanthamoeba. Two regions upon which efforts will be concentrated are the NH2-terminal region, which seems to have two deletions when compared with other actins, and CB-16, a 30 residue peptide that contains methyl lysine. The methylated position, which presumably corresponds to one of the three lysines in rabbit muscle actin CB-16, seems to contain approximately equal amounts of mono- and di-methyl lysines. Sequence work on rabbit skeletal muscle myosin is focussed upon a 22,000 dalton CN Br fragment from the COOH-terminus of the heavy chain. This region is thought to exist as a two stranded coiled-coil, and the sequence should thus contain the 3-4-3-4 repeats that were seen in tropomyosin sequence. Preliminary results suggest that this pattern is violated in some parts of the molecule. The significance of this result for assembly and organization of the thick filament will be evaluated by building models of this fragment.